Re: RTE-FLOW: PF vs PHY_PORT

[Adrien Mazarguil <adrien.mazarguil@6wind.com>]

Hi Vivek,

On Wed, Aug 22, 2018 at 05:16:52PM +0530, Vivek Sharma wrote:
> Hi Devs,
> 
> I am trying to enable RTE-FLOW support on one of our platforms & having hard time in figuring out PF vs PHY_PORT differences and DPDK rationale for introducing these two distinct identities. 
> 
> Rte-Flow distinguishes between RTE_FLOW_ITEM_TYPE_PF & RTE_FLOW_ITEM_TYPE_PHY_PORT and
> 
>                                                RTE_FLOW_ACTION_TYPE_PF & RTE_FLOW_ACTION_TYPE_PHY_PORT.
> 
> 
> I am finding it difficult to justify the presence of both these types, when functionality & implementation wise, these look quite similar. I would really appreciate if you could illustrate the differences between above item & action types by taking some hardware/platform as reference.

Some devices, typically those with a single PCI bus address shared for all
ports (e.g. Mellanox ConnectX-3) expose all their physical ports to each
PF/VF instance [1], not the other way around. With these, PHY_PORT item and
action give the ability to select a nondefault physical port in a flow rule.

PHY_PORT cannot be specified on most devices with PF/VF dedicated to
physical ports, although their drivers should at least recognize 0 as a
supported index and ignore it.

Since devices can expose any number of PF/VF instances and physical ports,
this gives applications the ability to use both as matching criteria and/or
action target.

A higher level alternative to PHY_PORT and PF/VF items/actions is PORT_ID to
match/target DPDK port IDs, which users may find more convenient. One
drawback is that it only works with devices instantiated within DPDK.

PF/VF and PHY_PORT should be reserved for corner cases where PORT_ID cannot
be used. My advice is to implement PORT_ID and not bother with the others
since port IDs are what applications are familiar with.

[1] Although with CX3, individual ports can be disabled per VF, they remain
    "seen" by each instance.

-- 
Adrien Mazarguil
6WIND